Air from a normal earth atmosphere consists primarily of diatomic nitrogen (N2) followed by diatomic oxygen (O2), water vapor, argon, carbon dioxide, and other trace gases generally not harmful to humans or other mammals at normal concentrations. However, both outdoor and indoor air may also contain many contaminants, with indoor air generally being more contaminated than outdoor air due to outgassing of building materials and furnishings such as rugs. These contaminants may include pathogens, pyrogens, other airborne particulates, other gases, or other substances. Airborne pathogens may include viruses, bacteria, and spores from molds and fungi. Within context of this application, pyrogens are defined as chemical compounds that can be oxidized, and include such chemical compounds as methane, ethane, butane, propane, toluene, alcohols, and numerous other compounds that can exist as a gas at normal room temperatures and pressures. Airborne particulates may include dust particles, metallic powders, pollen, and droplets of liquids. Other gases may include contaminant gases not found in a normal earth atmosphere but which are not normally subject to additional oxidation as are pyrogens. Other contaminant substances may include items not normally considered to be particulates or gases, such as animal hair and dander, other natural or synthetic fibers, dust mites and the like. Animal hair and dander, and some other fibers are able to harbor virus, bacteria, spores, or other potentially harmful substances, as well as being allergens to some people. It is generally desirable to have efficient and effective means of removing these contaminants in various spaces and volumes, including spaces concurrently or intermittently occupied by humans, pets, other animals, or plants.
Germicidal action of ultraviolet radiation of wavelengths generally shorter than about 400 nanometers (nm) is well known. Interaction of such ultraviolet radiation with many pathogens, generally by a mechanism of breaking chemical bonds within a molecular structure of a pathogen, may kill the pathogen or render it incapable of infection or reproduction. Generally, only brief direct exposures of susceptible bonding sites of a pathogen are needed in order to break chemical bonds and obtain germicidal benefits of ultraviolet radiation. This germicidal action has been incorporated, by use of so-called germicidal lamps capable of producing such ultraviolet radiation, into a number of products, including, for example, those used for sterilization of medical instruments, or other products used for sterilization of combs, clippers, and other tools used by barbers and beauticians. One key disadvantage of ultraviolet radiation for its germicidal action is that ultraviolet radiation may be blocked, or shadowed, by objects between a source of ultraviolet radiation and key interaction sites (e.g., molecular chemical bonds) within pathogens against which germicidal action is sought. Shadowing effects can result from airborne particulates as small as dust particles, and, in some cases, pathogens themselves or even large molecules can provide a shadowing effect for key interaction sites on the same pathogen or molecule, depending upon orientations of pathogens or molecules relative to a source of ultraviolet radiation.
Many germicidal lamps found in relatively inexpensive ultraviolet sterilization products make use of a mercury gas vapor discharge, also called mercury plasma, within an inexpensive silica glass tube, to provide an ultraviolet lamp. At least two predominant ultraviolet wavelengths are emitted from mercury plasma. These include an emission at approximately 254 nm, known as UV-C, and another shorter, thus more energetic, wavelength emission at approximately 185 nm, the latter being within a range of wavelengths from approximately 100 to 200 nm known as vacuum ultraviolet, or VUV, also referred to by some as “very ultraviolet.” Although photons at 185 nm are more energetic than photons at 254 nm, total energy intensity of radiation emitted from mercury plasma at approximately 254 nm is typically about 25 times greater than total energy intensity radiated around 185 nm. When inexpensive silica glass is used for a lamp tube that contains a mercury plasma, ultraviolet radiation shorter than approximately 200 nm, including 185 nm emissions from mercury plasma, is strongly attenuated by the silica glass, but 254 nm radiation from mercury plasma is transmitted through the silica glass tube with very little attenuation.
In addition to its germicidal effects, ultraviolet radiation containing wavelengths near 254 nm also has an additional effect of accelerating breakdown, or disassociation, of ozone (O3) molecules back into diatomic oxygen molecules (O2) and atomic oxygen (O), an effect which is discussed more fully later herein with an explanation and disclosure of how this effect may be used in a novel application to achieve some objectives of the instant invention.
It is one object of the instant invention to take advantage of germicidal action of ultraviolet radiation to support germicidal purification of air within a treated area. It is a further objective of the instant invention to promote, for multiple reasons, in some embodiments and operational modes, turbulent airflow through a chamber or other region wherein air is exposed to ultraviolet radiation, with one purpose of turbulence being to cause tumbling of any pathogens in the air stream so as to increase likelihood that key interaction sites on or within pathogens will be exposed to ultraviolet radiation and not shadowed as described earlier herein.
It has been known for some time that ultraviolet radiation having a wavelength of approximately 100 nm to 200 nm can be used for generation of ozone. It does this by breaking bonds of diatomic oxygen molecules, leading to creation of freed oxygen atoms, some of which combine with diatomic oxygen molecules to form molecules of ozone. What has not been well recognized in literature, however, is that use of ultraviolet radiation to generate ozone can also lead to creation of another family of compounds that have come to be called ozonites, which are generally ozone reaction products. Ozonites are compounds that also have an oxidative capability similar to that of ozone, with some being more reactive than ozone, and some being less reactive than ozone. Ozonites thus have properties different from those of ozone alone, and different properties of various types of ozonites make it desirable to be able to separately control types and concentrations of ozonites, relative to concentrations of ozone alone, produced by use of ultraviolet radiation. Providing innovative means and methods by which relative production or removal of ozone and ozonites can be controlled are thus objects of the instant invention.
Another predominant ultraviolet emission line from a mercury plasma, namely that at approximately 185 nm, has been used in various applications for generation of ozone. However, in order to exploit 185 nm wavelength ultraviolet radiation from a mercury plasma for most practical applications, it is necessary to use a containment tube for the plasma that is made of a material transmissive to ultraviolet radiation at 185 nm wavelength. As noted earlier, silica glass attenuates 185 nm wavelength radiation very strongly. However, quartz remains relatively transmissive at this wavelength, with quartz of different purities and compositions having somewhat different transmissivities. Quartz tubes are also highly transmissive to 254 nm wavelength radiation resulting from mercury plasma. Thus, for generation of ozone and for various other purposes requiring shorter wavelength 185 nm ultraviolet photons, it has become a common practice to use mercury plasma ultraviolet lamps made with quartz tubes rather than silica glass tubes in order to permit transmission of more ozone-generating 185 nm wavelength radiation resulting from mercury plasma. However, other sources of ultraviolet radiation, including some lasers, having one or more wavelengths in a range of 100 to 200 nm could be used for generation of ozone and ozonites in various embodiments of the instant invention.
Quantity of ozone and, as discussed later herein, ozonites, produced from ultraviolet radiation as discussed above is somewhat a function of initial energy states or excitation of diatomic oxygen molecules and other constituents of air flowing through chambers wherein air is exposed to ultraviolet radiation having wavelengths sufficiently short to cause breakdown of diatomic oxygen molecules. These initial energy states are affected by air temperature, pre-excitation of oxygen molecules and other constituents in air by electric and magnetic fields present in an exposure chamber, and recent history of exposure of constituents of air to ultraviolet and visible radiation at multiple wavelengths. It is thus another object of the instant invention to exploit one or more of these means to enhance initial energy states of a portion of diatomic oxygen molecules and other constituents of air so as to enhance efficiency and yield of processes disclosed herein for using ultraviolet lamps and other features of the instant invention to create ozone and ozonites, and to control types of ozonites produced and concentrations of ozonites relative to concentrations of ozone produced for a given application.
Although, as noted above, it has become common practice to use quartz tube mercury plasma lamps for generation of ozone, and less expensive silica glass tube mercury plasma lamps for many germicidal applications, what has not been fully recognized and previously exploited in the art are relative roles of different ultraviolet wavelength regimes in generation of this separate class of compounds called ozonites. As inferred earlier, ozonites have useful properties and applications which can be complementary or separate from applications of ozone alone. These useful properties and applications of ozonites, beyond those of ozone alone, are explained further below.
Ozone molecules themselves are highly reactive leading to many uses in purification and sanitization of air, liquids, and surfaces, generally via oxidative reactions with contaminants, including pathogens and pyrogens. Reactions of ozone with many pathogens leads to an effect called lysing, wherein ozone causes an oxidation reaction with bonds of molecules in cell walls of many pathogens, leading to a rupture of their cell walls, resulting in breakup and demise of the pathogen. Reaction of ozone with many pyrogens is generally an oxidative reaction similar in its products to those of normal combustion (e.g., carbon dioxide, water vapor, and other oxides). Ozone is thus useful in breaking many pyrogen contaminants down into less reactive and harmless compounds. However, in high concentrations, ozone may cause respiratory irritation and other undesirable effects, in humans and pets. Also, ozone molecules are themselves unstable, having a half-life of only a few hours.
The highly reactive and short-lived nature of ozone molecules are both an advantage and a limitation of ozone depending upon how it is used for air purification. An advantage is that ozone may be used for a short-term, high concentration treatment (called a shock treatment) of an area, such as one or more rooms in a house, to obtain oxidative benefits of ozone when humans or pets are not present, with ozone concentration levels decaying rapidly to levels safe for humans and pets soon after generation of ozone is terminated. One objective of the instant invention is to provide a capability for generation of sufficient levels of ozone to permit use of ozone in providing such short term treatments of limited areas. It is another objective of the instant invention to provide a capability for quickly destroying residual ozone in an area so as to more rapidly reduce ozone concentrations to levels safe and comfortable for human habitation.
A limitation of use of ozone is that, due to ozone's high reactivity, it will tend to react quickly with substances nearest a source of ozone generation, so that concentrations fall off quickly with distance from an ozone generator. Its high reactivity and its instability also mean that ozone itself provides little long-term or residual beneficial oxidative effect in a treated area. However, it has been cited in ozone-related literature that some byproducts, called ozonites, of interaction of ozone with other molecules or substances in liquid or gaseous media are also capable of oxidative or other beneficial reactions. Ozonites resulting from interactions of ozone and atomic oxygen with constituents of a normal airflow through an ozone-producing generator, as might be typical of normal household air, are generally less reactive and more stable than ozone molecules, but some ozonites may be more reactive than ozone alone. For example, some ozonites include hydroxyl radicals as well as other ionized or non-ionized molecules that are more reactive than ozone itself. (Use of ozonites to create additional oxidative reactions has been called “advanced oxidation” or “advanced oxidation processes” by some authors in ozone-related literature.) Ozonites that are less reactive than ozone molecules tend to persist longer and propagate further from an ozone generating source than ozone molecules, and are thus capable of producing beneficial effects of oxidation of contaminants and pathogens for longer periods after generation, and at greater distances from a generator, than ozone alone. These less reactive ozonites are also generally less likely than ozone to cause irritation in exposed humans and animals (e.g., pets). In contrast, ozonites such as hydroxyl radicals that are more reactive than ozone will tend to react even more rapidly than ozone with pyrogens, pathogens, and other contaminants and thus tend to be even shorter-lived with less far-reaching effects than ozone alone. However, this more highly reactive class of ozonites has another very important benefit—namely, an ability to oxidize some compounds, particularly those known as refractory organics, defined below, that are generally less susceptible to oxidation by ozone alone, particularly at normal room temperatures and pressures.
Pyrogens may include refractory organics such as nitrobenzene, phenols, 2,4,6-trinitrotoluene (TNT), atrozine, chlorobenzenes, and other compounds that are generally less susceptible to direct oxidation by ozone and atomic oxygen at normal room temperature and pressure. It has been found that many of these refractory organics are susceptible to oxidation, at normal room temperature and pressure, by some ozonites, particularly those ozonites containing hydroxyl radicals, ozonites containing halogens, and other highly reactive forms. These highly reactive ozonites may be created by interaction of ozone (O3) or free atomic oxygen (O) with substances such as water vapor, hydrogen peroxide, or halogen molecules or compounds present in an air stream in which ozone is being created by VUV radiation, or in which ozone is being destroyed by UV-C radiation. Free atomic oxygen (O) may be created from breakdown of diatomic oxygen (O2) molecules by VUV radiation during creation of ozone, or during breakdown of ozone molecules by UV-C radiation.
Thus, in addition to obtaining sterilization benefits of ultraviolet radiation, and purification and sanitization benefits of ozone alone, it is an additional object of the invention to provide novel and unobvious features to promote generation of ozonites and, in some cases and applications, to enhance relative concentrations, in treated areas, of ozonites as compared to ozone alone.
Additionally, in different embodiments of the instant invention, or in different operational modes of a given embodiment, it is a further object of the instant invention to provide features for enhanced generation, in some cases, of ozonites less reactive than ozone alone, and in other cases, to provide additional novel and unobvious features to enhance generation of ozonites more reactive that ozone alone.
As will be shown later herein, generating enhanced concentrations of ozonites, as compared to ozone alone, is accomplished in the instant invention by novel, but simple, combinations, in one or more devices in different embodiments, of filters or humidifiers or injectors to pre-treat an incoming air stream, different types of ultraviolet lamps in one or more exposure chambers, carbon canisters or other post-exposure filters to post-process or treat an exiting air stream, one or more fans to move an air stream through a purification unit and help control whether airflow is laminar or turbulent within the unit, and control systems which may provide for multiple modes of operation. Pre-treatment of an air stream may involve use of filtration to remove larger fibers or larger particulates from the air stream. Pre-treatment may also involve evaporation or injection of water vapor, hydrogen peroxide, catalysts, or other substances into an incoming air stream in order to modify or control some reactions that take place within a purification unit of the instant invention or within an exiting air stream or within an area or volume being treated by a purification unit of the instant invention. Water vapor or other agents may be added via use of Seltzer pads that provide a medium for wicking and evaporation of selected substances into an air stream. Water vapor or other agents could also be added to an air stream via use of high-pressure atomizing nozzles, via use of ultrasonic action, as is common in some household humidifiers, via use of heating to produce steam or other vapors, or by other means.
In addition to contributing to creation of more reactive ozonites containing hydroxyl radicals, enhanced levels of water vapor in an output air stream, and consequently in an area being treated, will tend to cause spores of molds or fungal materials to open up, or bloom, causing them to be much more susceptible to reaction and destruction by ozone or ozonites in air. A similar effect is also generally true for biofilms.
Various combinations of ultraviolet lamps, including one or more lamps that provide ultraviolet wavelengths that tend to help produce ozone and/or including one or more lamps that produce wavelengths that tend to break down ozone, may be used simultaneously within a chamber, or sequentially along a flow path, or in an alternating fashion, perhaps controlled by a timer, in order to help control generation and destruction of ozone, and production of ozonites, within a purification unit of the instant invention. Carbon canisters or other devices may be used to treat an air stream in a post-exposure filtration or other post-exposure treatment after it has flowed through one or more chambers and been exposed to one or more ultraviolet lamps in order to control generation, destruction, or release of ozone, ozonites, or other substances within an air stream. Post-exposure treatment may be for a purpose of further controlling concentrations of ozone, ozonites, or other substances exiting a purification unit of the instant invention. Heat may be added, via an electrical resistant heater or another source of heat, in order to help control reaction rates that help lead to desired changes in an exiting air stream. Other parameters or conditions that determine efficiency of a purification unit of the instant invention in producing ozone or ozonites, or both ozone and ozonites, include dimensions of one or more exposure chambers containing ultraviolet lamps, particularly VUV lamps used in various embodiments, and whether airflow through such chambers is turbulent or laminar in the vicinity of ultraviolet lamps, particularly any VUV lamps used in various embodiments. Dimensions of exposure chambers are important to controlling relative proportions of ozone and ozonites produced since shorter wavelength VUV radiation used to produce ozone is attenuated in air much more than longer UV-C wavelength radiation, which tends to break down ozone. Thus, a chamber with smaller dimensions surrounding a VUV tube, nominally one to two centimeters, will tend to produce a higher output of ozone, and a higher concentration of ozone relative to ozonites. A chamber with larger dimensions will tend to permit relatively more exposure of ozone to UV-C radiation from either a VUV tube or from a germicidal tube which primarily produces UV-C radiation, leading to a greater reduction in output of ozone relative to various ozonites. In addition, a laminar flow of air over a VUV tube will tend to cause creation of a higher concentration of ozone since there is less opportunity for ozone created in a zone close to a VUV tube to mix with other constituents of air and undergo reactions leading to reductions in ozone concentrations and increases in ozonites concentrations. Turbulent flow, however, causes better mixing, with other constituents of an air stream going through an exposure chamber, of ozone created near a surface of a VUV tube, thereby reducing concentration of ozone and enhancing production of ozonites that contribute to advanced oxidation. Bladed fans will tend to produce more turbulent flow than squirrel cage blowers. Use of reflectors around a UV-C tube (i.e., germicidal tube) can increase exposure of ozone to reflected UV-C radiation, thus reducing concentration of ozone but increasing concentration of ozonites produced. Various controls, or an overall control system, may be used to control use or sequencing of individual components of any given embodiment of the instant invention. Any given embodiment may contain some or all components and appropriate controls for different modes of operation as described above and in more detail later herein in order to help optimize a given embodiment for a particular application or set of applications.
Different modes of operation take advantage of different effects of different wavelengths of ultraviolet radiation to independently promote generation or destruction of ozone relative to ozonites, and to add substances or remove substances from an intake air stream or an exiting air stream to further control types and concentrations of ozonites, ozone, and other products of reactions that take place within a purification unit of the instant invention. Destruction of ozone and control of relative concentrations of ozone and ozonites takes advantage of a property of UV-C radiation mentioned earlier, namely, an ability of UV radiation having a wavelength of approximately 254 nm to break bonds within an ozone molecule, resulting typically in creation of a diatomic oxygen molecule and freeing of an oxygen atom, which then reacts rapidly with other molecules or substances in air. Thus, various embodiments of the instant invention may be optimized for applications primarily related to removal of ozone rather than generation of ozone. For example, in some environments where ozone generators of various types may be used to provide relatively high concentrations of ozone in specific areas or substances, especially in a confined space occupied by humans or other animals or plants, release of ozone into ambient air from materials or substances being treated may cause ozone concentrations to exceed safe or desirable levels. This may occur, for example, in situations such as use of ozone to control growth of fungal organisms on grain stored within a warehouse or grain elevator, or use of ozone in a jetted hot tub or spa, as described in Applicant's U.S. Pat. No. 6,723,233, to control contaminants within water or within plumbing or other fixtures associated with a hot tub or spa. In such cases, embodiments of the instant invention may be used in a free-standing mode within ambient air from which ozone removal is desired, or embodiments may be tailored, for example, to interface with locations, such as vents, where ozone is released from materials or substances being treated so as to further increase effectiveness of ozone destruction or control. Such embodiments may make use of one or more standalone or integrated ozone sensors, such as revealed herein, to control operation of embodiments intended for ozone removal, or such embodiments may simply be controlled manually or by use of timers.
For some applications, to further control concentrations of specific ozonites or other compounds produced within or exiting from a purification unit of the instant invention, alternate vapor discharge or plasma lamps, or lasers, or other sources of radiation capable of producing different radiation wavelengths to disrupt molecular bonds in those specific ozonites or other compounds to be controlled may be selected and integrated into alternate embodiments of the instant invention. Such lamps may be based on substances other than mercury, or contain compounds in addition to mercury, that are capable of producing radiation of desired wavelengths. For containment tubes, such lamps may also use materials, other than silica glass or quartz, that have less attenuation at desired wavelengths.
Certain embodiments of the instant invention may also make use of hybrid ultraviolet tubes, such as disclosed in Applicant's U.S. Pat. No. 6,426,053, in order to obtain at least two additional benefits. Such hybrid tubes use a coil of wire wrapped in a helical fashion down the length of a plasma containment tube, generally made of quartz, to generate electric and magnetic fields. These fields create a theta pinch effect on plasma within the tube that enhances efficiency in generation of radiation from plasma in the tube by increasing collisions, within the pinched plasma, among ionized components of the plasma and by reducing collisions of charged particles contained in the tube with walls of the tube. Such collisions with tube walls cause non-productive loss of energy from plasma in the tube and also contribute to undesirable heating of walls of a containment tube. A secondary benefit of a hybrid tube is that electric and magnetic fields, which are most intense immediately adjacent to the wires surrounding a hybrid tube, also contribute to pre-excitation of diatomic oxygen molecules and other constituents of air being treated so as to enhance efficiency of generation of ozone and ozonites by VUV radiation being emitted from such a tube, which radiation is also most intense in areas immediately adjacent to the tube. Other benefits, applications, and alternative embodiments for hybrid tubes are described in the referenced patent.